In a typical cellular system, also referred to as a wireless communications network, wireless terminals, also known as mobile stations and/or user equipment units communicate via a Radio Access Network (RAN) to one or more core networks. The wireless terminals can be mobile stations or user equipment units such as mobile telephones also known as “cellular” telephones, and laptops with wireless capability, e.g., mobile termination, and thus may be, for example, portable, pocket, hand-held, computer-comprised, or car-mounted mobile devices which communicate voice and/or data with radio access network.
The radio access network covers a geographical area which is divided into cell areas, with each cell area being served by a base station, e.g., a Radio Base Station (RBS), which in some networks is also called “NodeB” or “B node” and which in this document also is referred to as a base station. A cell is a geographical area where radio coverage is provided by the radio base station equipment at a base station site. Each cell is identified by an identity within the local radio area, which is broadcast in the cell. The base stations communicate over the air interface operating on radio frequencies with the user equipment units within range of the base stations.
In some versions of the radio access network, several base stations are typically connected, e.g., by landlines or microwave, to a Radio Network Controller (RNC). The radio network controller, also sometimes termed a Base Station Controller (BSC), supervises and coordinates various activities of the plural base stations connected thereto. The radio network controllers are typically connected to one or more core networks.
The Universal Mobile Telecommunications System (UMTS) is a third generation mobile communication system, which evolved from the Global System for Mobile Communications (GSM), and is intended to provide improved mobile communication services based on Wideband Code Division Multiple Access (WCDMA) access technology. UMTS Terrestrial Radio Access Network (UTRAN) is essentially a radio access network using wideband code division multiple access for user equipment units (UEs). The Third Generation Partnership Project (3GPP) has undertaken to evolve further the UTRAN and GSM based radio access network technologies. Long Term Evolution (LTE) together with Evolved Packet Core (EPC) is the newest addition to the 3GPP family.
Emerging mobile network trends may call for denser deployments in urban areas, due to increasing traffic and/or user density. Operators are looking to deploy smaller cells (e.g., pico and femto cells) in the same areas as macro cells, with varying degrees of “cooperation” and/or integration between them according to the desired level of network performance (so-called “HetNet deployments” or heterogeneous network deployments). A significant issue in such deployments is to provide increased/optimum mobility to UEs (user equipment nodes, also referred to as wireless terminals) that have different capabilities while providing/ensuring a reduced/lowest level of core network (CN) involvement, to reduce signaling traffic.
In WCDMA (Wide Band Code Division Multiple Access) systems, a user equipment that supports 3GPP Release 9 or later releases may be able to provide specific measurements to support mobility towards femto cells. In particular, these user equipments may be able to improve mobility towards closed HNB (Home Node B) cells, also known as CSG (Closed Subscriber Group) cells, by providing a Proximity Indication and specific System Information measurements that allow the serving RNC (Radio Network Controller) to disambiguate the target cell and to trigger the appropriate relocation procedures towards the right target. It has to be noted that the term Serving RNC (SRNC) can refer to either a HNB or an RNC.